Flor N, Harmon P, Datnoff L, Raid R, Nagata R
Department of Plant Pathology, University of Florida, Gainsville.
Everglades Research and Education Center, University of Florida, Belle Glade.
Plant Dis. 2008 Nov;92(11):1586. doi: 10.1094/PDIS-92-11-1586A.
Brown ring patch is a newly described disease of cool-season turfgrass first reported in Japan on creeping bentgrass (Agrostis palustris) (2) and later reported in California on annual bluegrass (Poa annua) (1). The disease is characterized by either patches or rings of discolored to blighted turfgrass that can range from a few centimeters to a meter in diameter. Affected turfgrass plants turn chlorotic and can be blighted from the crown to the leaf tips. Blight symptoms have been associated with fluffy white-to-cream aerial mycelium after extended incubation of the sample. Symptoms including patches of blighted turfgrass approximately 10 cm in diameter were observed on roughstalk bluegrass (Poa trivialis) that had been overseeded onto a dormant 'Tifdwarf' bermudagrass (Cynodon dactylon) putting green in Palatka, FL. A sample was submitted by the superintendent in June 2005 because symptoms were confused with dollar spot and a fungicide resistance issue was suspected. The sample produced abundant aerial mycelium after incubation. The pathogen was isolated on potato dextrose agar amended with rifampicin (100 ppm) and streptomycin (100 ppm) from Poa plants surface disinfested with 70% ethanol for 30 s. Colony and sclerotia morphology were consistent with Waitea circinata var. circinata as previously described (1,2). The teleomorph W. circinata var. circinata was not observed on plant material or culture plates. Amplified fragments of rDNA including internal transcribed spacers from the isolate were sequenced bidirectionally from four bacterial clones. The consensus sequences (GenBank Accession Nos. FJ029103, FJ029104, FJ029105, and FJ029106) matched with 99% homology (99% sequence overlap) isolate TRGC1.1 of W. circinata var. circinata described by Wong, NCBI Accession No. DQ900586 (1). Pots of 'Cypress' roughstalk bluegrass that were 1 week postemergence were inoculated with the pathogen using 10 infested wheat grains. Plants were incubated at 25°C in a sealed plastic bag with a moist paper towel in the bottom. Hyphae grew from the grains and colonized the grass. Individual plants began to turn chlorotic within 3 days and greater than 90% of the turf in pots was dead after 1 week. The fungus was reisolated from affected plants. Control pots were inoculated with uninfested wheat grains and showed no disease symptoms after 1 week. Inoculations were repeated twice more with the same results. To our knowledge, this is the first report of brown ring patch on P. trivialis in Florida. References: (1) K. A. de la Cerda et al. Plant Dis. 91:791, 2007. (2) T. Toda et al. Plant Dis. 89:536, 2005.
褐色环斑病是一种新描述的冷季型草坪草病害，最早于日本在匍匐翦股颖（匍匐翦股颖）上报道（2），后来在加利福尼亚一年生早熟禾（一年生早熟禾）上报道（1）。该病的特征是草坪草出现变色至枯萎的斑块或环带，直径从几厘米到一米不等。受影响的草坪草植株变黄，从叶冠到叶尖可能枯萎。在样本长时间培养后，枯萎症状与蓬松的白色至奶油色气生菌丝体有关。在佛罗里达州帕拉特卡，在休眠的“Tifdwarf”狗牙根（狗牙根）果岭上补播的粗茎早熟禾（粗茎早熟禾）上观察到了直径约10厘米的枯萎草坪草斑块症状。由于症状与美元斑病混淆且怀疑有杀菌剂抗性问题，草坪主管于2005年6月提交了一份样本。样本培养后产生了大量气生菌丝体。病原菌从用70%乙醇表面消毒30秒的早熟禾植株上分离，培养于添加了利福平（100 ppm）和链霉素（100 ppm）的马铃薯葡萄糖琼脂上。菌落和菌核形态与先前描述的圆核龟甲藻变种圆核龟甲藻一致（1,2）。在植物材料或培养皿上未观察到有性态圆核龟甲藻变种圆核龟甲藻。从分离物中扩增出包括内部转录间隔区的rDNA片段，从四个细菌克隆进行双向测序。共有序列（GenBank登录号FJ029103、FJ029104、FJ029105和FJ029106）与黄描述的圆核龟甲藻变种圆核龟甲藻分离物TRGC1.1具有99%的同源性（99%的序列重叠），NCBI登录号DQ900586（1）。出土1周的“柏树”粗茎早熟禾盆栽用10粒受侵染的小麦粒接种病原菌。将植株在25°C下置于底部有湿纸巾的密封塑料袋中培养。菌丝从麦粒生长并侵染草。单个植株在3天内开始变黄，1周后盆栽中超过90%的草坪死亡。从受影响的植株中重新分离出真菌。对照盆栽接种未受侵染的小麦粒，1周后未出现病害症状。接种重复进行两次，结果相同。据我们所知，这是佛罗里达州粗茎早熟禾上褐色环斑病的首次报道。参考文献：（1）K. A. de la Cerda等人，植物病害91:791，2007。（2）T. Toda等人，植物病害89:536，2005。
